Field of the Invention
The present invention relates to a tape measure and, in particular, to a tape measure provided with a disc brake mechanism.
Description of the Related Art
Tape measures generally include a measuring tape coiled about a tape reel disposed within a housing. A hook mounted on a free end of the measuring tape extends through a slot in the housing. This allows a user to extend the measuring tape outwardly of the housing in order to take a measurement using measuring indicia displayed on the measuring tape. In spring loaded tape measures, a spring mechanism biases the tape reel to retract the measuring tape into the housing to facilitate transport and storage of the tape measure. Spring loaded tape measures are therefore also provided with a locking mechanism to prevent retraction of the measuring tape while a measurement is being taken.
Conventional locking mechanisms include an abutment member which is movable between a released position and an engaged position. Typically the abutment member is actuated by a lever disposed near a top of the housing. In the released position, the abutment member is spaced-apart from the measuring tape and does not restrict extension or retraction of the measuring tape. This allows a user to extend the measuring tape outwardly of the housing to take a measurement. In the engaged position, the abutment member abuts the measuring tape against a bottom of the housing and restricts extension and retraction of the measuring tape. This prevents the measuring tape from retracting into the housing while a measurement is being taken. The locking mechanism is released, after the measurement is taken, to allow the measuring tape to retract into the housing. The locking mechanism accordingly controls retraction of the measuring tape into the housing.
However, conventional locking mechanisms do not control the rate at which the measuring tape retracts into the housing when the locking mechanism is released. This is because the locking mechanism can only be in the engaged position where retraction of the measuring tape is arrested, or the released position where retraction of the measuring tape is not arrested. The measuring tape of a spring loaded tape measure may therefore freewheel into the housing when the locking mechanism is released. This may cause the hook at a free end of the measuring tape to break off or otherwise damage the measuring tape.
U.S. Pat. No. 6,467,182 issued on Oct. 22, 2002 to Usami discloses a tape measure provided with a braking mechanism for controlling the rate at which a measuring tape retracts into the housing. A brake shoe contacts an outer circumferential part of a tape reel to apply a braking force which restricts rotation of the tape reel. This may prevent inadvertent retraction of the measuring tape.
Yet there still remains a need for improved locking mechanisms for a spring loaded tape measure.